The present invention refers to a plate heat exchanger for heat transfer between two fluids, comprising several abutting thin heat transfer plates and arranged between the heat transfer plates sealing members, which in alternate plate interspaces delimit a flow space for a first fluid and in the remaining plate interspaces delimit flow spaces for a second fluid, each heat transfer plate having a pressed corrugation pattern, which has two distribution portions and, arranged between said distribution portions, a main heat transfer portion, which is divided into several areas with parallel ridges and valleys, the plate heat exchanger having inlets and outlets for said fluids, arranged in such a way that the fluids will have a flow direction, between the heat transfer plates, essentially from one to the other of the distribution portions of each heat transfer plate.
From GB 1468514 a plate heat exchanger for heat transfer between two fluids is previously known, which is assembled from several heat transfer plates arranged such that the fluids flow on both sides of the plates. The heat transfer plates have a pressed corrugation pattern with an upper distribution portion and a lower distribution portion and, arranged between the distribution portions, a main heat transfer portion. The heat transfer portion comprises a pressed corrugation pattern with parallel ridges and valleys and is formed with several band like areas, extending along the plates. Between the heat transfer plates sealing members are arranged, which in alternate plate interspaces delimit a flow space for a first fluid and in the remaining plate interspaces delimit flow spaces for a second fluid.
From GB 1339542 a plate heat exchanger for heat transfer between two fluids is previously known, which is assembled from several heat transfer plates so arranged that fluids flow on each side of the plates. The heat transfer plates show two distribution portions and, arranged between the distribution portions, a main heat transfer portion. The heat transfer portion comprises a pressed corrugation pattern with parallel ridges and valleys and is formed with several band like areas, extending across the plates.
Despite the fact that the previously known plate heat exchangers show heat transfer portions formed with several areas, which extend across or along the plates, a problem occurs in that the plates are deformed. I.e. the plates bend or bulge in different directions. Thus, the plates become difficult to handle, e.g. during mounting on a conventional carrying bar or during welding of the plates.
The problem stems from the fact that a strong corrugation of the heat transfer portion of the plates admits an elongation of the plates in said portion. This problem occurs especially when the parallel ridges and valleys have a small angle compared to an imaginary axis around which the plate may have a risk of being curved, simultaneously as the remaining parts of the plate, e.g. sealing grooves or portions of the ports, cannot give sufficient rigidity to restrain the deformation.
The object of the present inventions is, in a plate heat exchanger of the kind described, to achieve a heat transfer plate in which the corrugation pattern is so shaped that the risk of deformation decreases so that handling of the heat transfer plates is enhanced compared with previously known heat transfer plates.
According to the invention these objects are achieved by a plate heat exchanger of the introductory kind described, which is characterised in that the heat transfer portion of each heat transfer plate comprises a row with at least three areas, located following one another in said flow direction, that an even number of such rows are arranged adjacent to each other across the flow direction, and that the parallel ridges and valleys of each pair of adjacent areas extend in such a way, that they form mirror images of each other with reference to an imaginary line between respective areas.
The invention is also applicable for other types of plate heat exchangers and refers also to a heat transfer plate for a plate heat exchanger, comprising inlets and outlets, for at least two heat transfer fluids and, arranged between the outlets, a heat transfer portion, the inlets and the outlets being arranged so that said fluids will have a flow direction essentially from respective inlet to respective outlet, the heat transfer portion being provided with a pressed corrugation pattern which is divided into several areas having parallel ridges and valleys, characterised in that the heat transfer portion comprises a row with at least three areas located after each other in said flow direction, and that an even number of such rows is arranged next to each other across the flow direction, and that the parallel ridges and valleys of each pair of adjacent areas extend in such a way that they form mirror images of each other with reference to an imaginary line between respective areas.